The Principle of Sufficient Reason: A Reassessment

by Alexander R. Pruss

The Principle of Sufficient Reason (PSR) says that all contingent facts must have explanation. In this 2006 volume, which was the first on the topic in the English language in nearly half a century, Alexander Pruss examines the substantive philosophical issues raised by the Principle Reason. Discussing various forms of the PSR and selected historical episodes, from Parmenides, Leibnez, and Hume, Pruss defends the claim that every true contingent proposition must have an explanation against major objections, including Hume's imaginability argument and Peter van Inwagen's argument that the PSR entails modal fatalism. Pruss also provides a number of positive arguments for the PSR, based on considerations as different as the metaphysics of existence, counterfactuals and modality, negative explanations, and the everyday applicability of the PSR. Moreover, Pruss shows how the PSR would advance the discussion in a number of disparate fields, including meta-ethics and the philosophy of mathematics.

Genres: Philosophy, Metaphysics, Theology, Religion

350 pages, Hardcover

First published March 20, 2006

About the author

Canadian philosopher, mathematician. Pruss's philosophical thought reflects Christian orthodoxy. He is a Roman Catholic and a member of the Society of Christian Philosophers.

Pruss defends the principle of sufficient reason (PSR), claiming that it is self-evident, and arguing that the rejection of PSR creates problems in epistemology, modality, ethics, and even evolutionary theory.

Pruss is a critic of David Lewis's "extreme modal realism," and instead gives "a combined account" of Leibnizian and Aristotelian modality, which integrates the "this-worldly capacities" of the Aristotelian view and Leibniz's account of possible worlds as thoughts in the mind of God.

Reviews

[Nelson · Rating 4 out of 5]

This is a good book. Very technical so I would only recommend this to those who are highly educated in philosophy and who have a decent grasp of formal logic. I absolutely would not recommend this to a beginner who is looking into the PSR.

In the first section, Pruss offers a detailed history and definition of the PSR. In the second section, he thoroughly explores various attacks on the PSR and meticulously deconstructs, critiques and refutes them. In the third, he offers justifications/assesses various justifications of the PSR.

Sections one and two were brilliant, but two was little tedious (perhaps reasonably so as the critiques of the PSR were technical and required a requisitely technical response). But I do think he put a bit too much stock in the objections than was proportional to their force however and he was too modest in his rejection of them.

Section 3 was a decent defence of the PSR however it was very very modest (and characteristically technical). He explores various arguments for the sufficiency of the PSR (and assesses the plausibility of them also). He also provides defences to the criticisms of those justifications and assesses their ultimate plausibility. The conclusion, it should be noted, was unduly modest in my opinion (but perhaps that’s because I simply lack a deep appreciation for the force of the objections).

In all a good book that does a very thorough job of defending and justifying the PSR. Truly an essential work on the subject and deserving of high praise for its depth and for the genius of the author. But if you are looking for a dramatic and compelling defence of the PSR I would look elsewhere. I realistically won’t read this book again (although I liked it). I much prefer the book ‘Necessary Existence’.

[Darius Luca · Rating 5 out of 5]

Pruss presents a wonderfully complex presentation of the PSR, and defends it - successfully, I'd say. There's a lot to say (of course, the book is quite long), but here are my most important reflections.

The discussion of the modal collapse argument, as per van Inwangen, which is probably the biggest and most elegant objection to the PSR, is graciously 'dissected' by Pruss. He offers relevant counterexamples to the most important premise, not giving up on the BCCF in the process, but he also doesn't shy away from, at times, admitting that there might still be gaps in his own view which must be filled.

Pruss also discusses quantum events and explains why we shouldn't abandon the PSR because of them, though I was more interested in the metaphysical 'bread and butter' that is found in this book.

I also found the arguments he gave in favour of the PSR compelling. Admittedly, some of them might just collapse to intuitionistic reasoning, however the PSR is one case where intuition, explanatory power and even relevance in modal reasoning seem to go hand in hand. That is to say, if one accepts that everything contingent seems to have a cause, he (or she) probably does so not because we have somehow evolved to have this (hypothetically) demonstrably wrong intuition, but because cases of something occurring causelessly seem either exceptionally rare or impossible.

Moreover, Pruss rightly points out that we eventually will need an account of causality on any modal view. And the PSR not only offers a simple and even elegant account of causality (as opposed to virtually any rival hypothesis), but for anybody who holds to a roughly Aristotelian view, including the PSR into such a modal account becomes very easy and gains explanatory power for the account.

I won't spend too much time talking about this as a lot of the content here is pretty abstract and thus difficult to compress, but the section on Causal Principles was also quite insightful and offers a new way to reach the PSR or a related conclusion.

All this being said, the language he uses in the book is, at times, quite convoluted and even a bit opaque, so that even considering the examples he regularly gives you might have to grapple with the concepts for quite a bit. Still, I found the book very insightful. This book might be one of the reasons why the discussion on the contingency argument has shifted from the PSR to the BCCF and the stage two cosmological argument, or what Pruss calls the 'gap problem' in his contribution in the Blackwell Companion to Natural Theology.

[Adam Chandler · Rating 4 out of 5]

Pruss argues the the Principle of Sufficient Reason (PSR) exists despite things like the modern philosophical objects from free will and the physical objections from quantum mechanics. He does good work in addressing the concerns and shows that no objection is a defeater of the PSR but I find his support for the PSR is somewhat lacking. Pruss brings forward a number of logical arguments for the PSR but they are not definitive, as he admits, so he relies on the self-evident claim that everything has a cause except for something necessary. It is my hope to find something more concrete to support the PSR. At the very least, this book is incredibly useful in understanding the PSR in relation to causation in philosophical conversation today.

[Jared Mindel · Rating 4 out of 5]

Very good. I only give it 4 stars because some of it could be much clearer.